1. Field of the Invention
The present invention relates to a hydraulic cylinder apparatus of a type in which a hydraulic cylinder is actuated for extension by an oil pressure produced in an intensifier such as a pneumatic/hydraulic booster.
2. Description of Prior Art
A known hydraulic cylinder apparatus of the type actuated by a booster is disclosed in the Japanese Patent Laid Open Publication No. 1987-282808. This hydraulic cylinder apparatus was previously proposed by one of the assignees of the present invention and constructed as illustrated in a schematic view in FIG. 12.
As illustrated in a vertical sectional front view in FIG. 12(a) and in a plan view in FIG. 12(b), a pneumatic/hydraulic booster 232 is horizontally disposed in a space above a hydraulic cylinder 230 disposed vertically, and an oil make-up tank 247 of the type pneumatically pressurized is disposed in a lateral space beside the hydraulic cylinder. A plunger chamber 239 of the booster 232 is connected in communication with an extension cylinder chamber 235 of the hydraulic cylinder 230 through a pressurized oil supply/discharge piping 290, and an oil make-up chamber 248 of the tank 247 is connected in communication with the plunger chamber 239 through an oil make-up piping 291.
There are, however, the following problems associated with the above prior art.
Since both the left and right end portions of the booster 232 project outwardly beyond the external peripheral surface of the hydraulic cylinder 230, the hydraulic cylinder apparatus 226 has a large outer diameter dimension M.
Further, since there are provided two pipings, namely the pressurized oil supply/discharge piping 290 and the oil make-up piping 291, the length of the piping line becomes long, increasing the air stagnation capacity within the piping line, but also the number of pipe fittings becomes large and increases the air stagnation capacity at stepped portions within the pipe fittings. Therefore, it becomes difficult to remove air working at the time of trial operation of the hydraulic cylinder apparatus 226 and at the time of starting its utilization after the completion of overhaul/maintenance.
For solving the above-mentioned problems, the inventors of the present invention proposed the hydraulic cylinder apparatus 126 illustrated in FIG. 11 prior to the proposal of the present invention.
In this apparatus 126, a booster 132 is disposed in such a manner that a plunger chamber 139 faces downward, and a lower end wall 140 of the plunger chamber 139 is fixedly secured to an upper wall 137 of cylinder chamber 135 of a hydraulic cylinder 130. An oil make-up chamber 148 is disposed in such an annular manner as to encircle the outer periphery of the plunger chamber 139.
The hydraulic cylinder apparatus 126 according to this prior invention example has the following advantages.
An outer diametral dimension of the hydraulic cylinder apparatus 126 can be defined within an outer diametral dimension "d" of the booster 132. When being compared with the dimensions of the conventional embodiment illustrated in FIG. 12, although a height dimension "H" thereof is approximately 3/2 times, an outer diametral dimension thereof can be approximately 1/2 times. Therefore, the space occupied by it can be made smaller, e.g., about 3/8ths as much.
Further, since the plunger chamber 139 and the cylinder chamber 135 are vertically connected in communication to each other, the pressurized oil supply/discharge piping 290 of the conventional embodiment can be omitted. Since the piping line can be shortened, the number of the pipe fittings can be decreased correspondingly and removal of air from the apparatus becomes easy.
Some room for improvement remains in making the hydraulic cylinder apparatus 126 small, which might be attained by decreasing the height dimension "H" thereof.